Aug/Sept 2012 Tech Tip

This post for August / Sept., covers photos #12 through # 17, of a Stihl O 28 Wood Boss that came to the shop with an oil leak, general maintenance.

Two defects were present after initial inspection of the unit: (1) black oil from the leak all over power unit, (pic #12) and (2), defective oiler reservoir cap / gasket, that allowed the leak to progress over some years of ownership.

(Pic #12) also shows a pan of black, used auto engine oil I drained from the oiler reservoir; a definite “no-no”, due to combustion impurities contained in the oil, along with what would be left of the additive package.  Either of which causes oiler pump / “o” ring / gasket damage.

The oiler reservoir was not completely sealed on the cap end, allowing “chain oil” to leak from the threaded end as well as from the pump side. This defect can be likened unto a soda straw filled with liquid, the straw being the oiler reservoir in this example. When you seal your finger over the top end of the straw, as the oiler reservoir cap should have, nothing flows from the bottom of the straw, until you remove your finger. Since the oiler cap was compromised from deformation, there was no adequate seal to keep the contents in the tank, so oil flowed from under the cap as well as from the pump end. Like removing your finger from the straw. Remembering,that gravity always wins……… well, most of the time. 

Remaining photos, demonstrate the importance of complete component cleaning prior to reassembly of the customer’s unit, (pic #13 > pic #17). Of importance, is component separation in pans or other vessels, that will allow organization of each system; ie. starter, ignition, shrouding, fuel / handle systems and related fasteners. This method of organization beats the normal practice of just tossing stuff onto the benchtop, hoping to find “everything” later. I guess what’s left-over could always go into the fuel tank?

After reassembly, there’s always the cutting attachment to service. Bar grooves will be cleaned and a bar groove gauge will measure the inside clearance and rail uniformity. Removal of sawdust from the tailpiece oil holes, along with checking  overall straightness. Check the tip for any deformation and lube the sprocket tip both sides if applicable. Then, we sharpen cutters & set the depth controls,(sometimes called rakers), checking for chain “stretch”, that alters chain pitch. Often times “stretch”can be accelerated not only by over tightening / overheating, but also by using improper chain lubricant, such as used engine oil, which is absent adhesive agents that keep the bar and chain lubricated as the chain travels around the bar.  Stay tuned and many thanks for stopping by. Be well…….Shade Tree Mechanic. 


One response to “Aug/Sept 2012 Tech Tip

  1. Glad you enjoyed my two year old posts. I haven’t made insertions since the date of those you read, so guess I will have to set about relearning how to navigate my own website with respect to new material and pix. Give me a few days, Sir. I have several saved photos of service jobs, common to power equipment, from which every day users will benefit. My concern as an independent servicing dealer, is giving tips to those I will never meet, concerning pitfalls people will experience with the care & feeding of their handheld / wheeled / stationary equipment. So much of what people pay for, regarding legitimate service failures, is preventable. I’d say conservatively 80%. Shops are in business to make money on peoples’ misfortunes, when something quits or breaks, so expect to “pay” for repairs. Given the ethanol percentages contained in fuels used by consumers, a large portion of those misfortunes is preventable by the consumer and can be easily remedied via common sense, if the equipment is free of component damages after a given failure. All or most of the service work I perform is fuel system-related. Aside from normal wear on blades, saw chains, etc. The “normal” consumer would be well-served, if he or she adopted maintenance procedures such as those utilized by loggers, who depend on their chain saws for daily performance with little or no downtime from carelessness and neglect. They are preventive maintenance users, as their paychecks depend upon a sharp saw that performs. Just some thoughts. Hope this finds you well and many thanks for your interest! “Shadetree”…….

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